According to WHO statistics, 8-10% of all married couples consult medical professionals after failing to conceive. Over 40 million couples are currently being treated for infertility. Among these infertile couples, it is estimated that the infertility in 40% of the couples is due to male originating causes, and another 20% is due to combined male and female originating causes. Semen analysis is a major technique in evaluating male originating causes.
Standard semen analysis protocol involves the determination of at least three major semen parameters:
1. total sperm concentration (TSC);
2. percentage of motile sperm; and
3. percentage of normal sperm morphologies.
For all practical purposes, semen analysis, a key factor in human male fertility medicine, has not changed since the 1930's and is still done today by microscopic inspection. In fact, it is one of the very few remaining in vitro, body fluid analysis still performed almost solely via manual methods.
This manual methodology involves carefully observing the sperm cells, counting them to determine their concentration, classifying their motility, identifying their morphology, etc. This work requires high expertise, is very labor intensive and if done according to standard protocols, takes at least an hour per test.
Manual assessments are known to be quite inaccurate due to numerous sources of error. The main sources of error are:    Subjectivity of the observer.    The varying criteria used in the different labs and by different observers.    The large statistical errors due to the limited number of sperm analyzed.
The WHO manual (WHO laboratory manual for the examination of human semen and sperm-cervical mucus interaction. 4th edition, Cambridge University Press, 1999) recommends observing not less than 200 sperm and classifying the morphology and motility of each. This itself is an error introducing procedure due to the tediousness and time consuming nature of the task. In practice, 50 to 100 sperm cells at most are analyzed. Even if the observer introduces no errors, the statistical error alone reaches tens of percentages.
As a result of the above methodology, semen analysis test results are globally recognized to be highly subjective, inaccurate and poorly reproducible. Inter lab and inter technician variations are of such proportions that this issue is of major concern in male fertility medicine and the unresolved subject of discussion in the vast majority of symposiums, congresses and conventions on the subject.
In order to overcome these difficulties, medical instrumentation companies have introduced dedicated computerized systems based on image analysis (CASA—Computer Assisted Semen Analyzers). These systems require an extremely high quality image because all their results are based on image processing. Although these systems have attempted to replace manual analysis and establish industry accepted standards, they have not succeeded in either of these objectives.
The first objective could not be achieved because analysis results continue to be dependent on manual settings and on the different makes of equipment. Replacing routine manual analysis is totally impracticable because the systems are extremely expensive, complex and difficult to use. The fact is that such systems are generally not found in routine semen analysis but have rather established their niche almost solely in research centers, university hospitals and occasionally in highly specialized fertility centers.
An additional approach for semen measurements is described in U.S. Pat. Nos. 4,176,953 and 4,197,450, whose entire contents are incorporated herein. These patents describe a method for measuring sperm motility using electro-optical means and an analog signal analyzer. A suspension of sperm cells is continuously examined in a predetermined field in order to detect variations in optical density by the motion of the sperm. An amplitude-modulated analog electrical signal is generated in response to the variations, and the peaks and valleys of this signal are counted over a predetermined time period to provide an abstract parameter termed Sperm Motility Index (SMI). This parameter is related to motility and gives readings which are proportional to the number of motile cells multiplied by their respective velocity.
An automatic sperm analyzer called the Sperm Quality Analyzer (SQA), which provides the SMI parameter, has been on the market for a number of years. The analyzer is used in the following manner: a sperm specimen is taken up by a disposable chamber which has a rubber bulb at one end to aspirate the sample, and a thin measuring compartment at the other end. After aspirating the sample, the measuring compartment is inserted into the SQA and the SMI of the sample is automatically determined. The SMI parameter, although useful in some applications, was not significantly accepted by the medical community as a viable alternative to the conventional microscopic semen measurements.
It is common knowledge that in some fields of veterinary fertility analysis, total sperm concentration (TSC), is evaluated by measuring optical turbidity of the specimen. The physical principle behind this approach is that sperm cells are more opaque than the surrounding seminal plasma, and absorption of a light beam by the specimen is therefore proportional to the TSC.
For example, U.S. Pat. No. 4,632,562 discloses a method of measuring sperm density by measuring the optical absorbance of a sperm containing sample and relating the absorbance output signal to the density by using at least three summing channels. The disclosed method is intended for use in artificial insemination in the cattle breeding industry, and measures the optical absorbance in the range of 400-700 nm.
This technology however, has not and could not be adopted for human use for the following reasons:
(1) Human sperm concentrations in the normal range (and even in higher than normal cases), are more than an order of magnitude lower than in most of their veterinary counterparts—where this technology has been adopted.
(2) Human cases are treated even when sperm concentrations are far below their normal levels. This of course is not the case for animals. Infertile animals are normally culled—in any case, they are not treated for infertility.
(3) TSC in humans is a parameter, which in itself, is totally insufficient for fertility investigations, and microscopic analysis is in any case required for all the other data in the standard semen analysis protocol. To a large degree, this also holds for veterinary applications. This fact made optical absorption measurements superfluous, and no real effort has been invested in this field.
There is thus a need for a simple, objective technique for measuring TSC in human semen.
According to the WHO manual, sperm motility assessment (considered by most to be the most important single semen parameter) can be carried out manually using a grid system under the microscope or, alternatively, by use of CASA.
CASA provides some advantages over manual methods. However, accuracy and provision of quantitative data are totally dependent on precise semen preparation techniques and instrument settings. These factors (high expertise and sophisticated environment) along with the prohibitive cost of such instrumentation, rule out for all practical purposes their application for routine semen analysis.
U.S. Pat. No. 4,896,966 discloses a motility scanner for characterizing the motion of sperm, bacteria and particles in fluid. The scanner comprises an optical system including a collimating lens, condensing lens, imaging lens and a pair of reflecting elements, a source of illumination, radiation sensing means, signal processing means, and display means. The imaging lens has a useful depth of field at its object plane of at least about 0.2 mm.